In the process of coding digital high definition video data for transmission, the video data may be compressed and transmitted in a layered coded format. The layered format may incorporate header data identifying data segments such that, upon loss of data during transmission, a receiver can find an appropriate re-entry point in the received data stream. Extra protection against lost or corrupted data causing confusion or disrupted service at the receiver can be provided by arranging coded video data in transport blocks. The transport blocks include additional header data identifying relatively small portions of the video data. The header data advantageously may include pointers which indicate data re-entry points within respective transport blocks.
The video data may be compressed in a variety of ways, such as in MPEG format or a similar format. MPEG is a standardized coding format being established by the International Organization for Standardization. The standard is described in the document "International Organization for Standardization", ISO/IEC DIS 11172, Coding of Moving Pictures and Associated Audio for Digital Storage Media, Rev. Nov. 23, 1991, which document is incorporated herein by reference for description of the general code format. A system which processes a high definition television signal advantageously using MPEG-like processing and video data transport blocks with associated headers is described in copending U.S. patent application "Apparatus for Segmenting Encoded Video Signal for Transmission", A. A. Acampora et al., Ser. No. 814,207. In that system, a transport processor is used to form data words into data packets which constitute a transport block. The transport processor also generates the required headers, and merges headers with the appropriate transport block.